Semiconductor image sensors developed and enhanced in various forms significantly widen the fields of application of photographing apparatuses such as cameras.
The most popular semiconductor image sensors include charge-coupled device (CCD)-type image sensors and complementary metal oxide semiconductor (CMOS)-type image sensors. Recently, along with the significantly improved performance of CMOS devices, CMOS-type image sensors have been applied to a wide range of fields. Pixel integration of such semiconductor image sensors is rapidly increasing through repeated innovations, and thus even small semiconductor image sensors are now capable of picking up very high resolution images.
In correspondence to such high-pixel image sensors, high-quality lens optical systems suitable for the image sensors are demanded. It is necessary for a high-quality lens optical system to exhibit low aberration and high sharpness at all regions.
To obtain a fine quality image, not only a high-quality image sensor as described above, but also a lens optical system suitable for the high-quality image sensor is needed.
It is necessary to maintain a high performance and reduce the size of lens optical systems applied to general small cameras, e.g., lens optical systems applied to small cameras for mobile phones or vehicle cameras. A general lens optical system has a structure in which a plurality of lenses are arranged on a single optical axis, where the lenses include one or more glass lenses for securing a fine optical performance. Particularly, from 5 to 6 glass lenses are applied to a vehicle camera. However, a glass lens is expensive to manufacture and size reduction of a lens optical system is limited due to limits in forming/manufacturing glass lenses.
Thus, there is still a demand for a lens for a small camera, which has a higher optical performance than demanded by an optical design thereof, may be easily downsized due to ease of formation/manufacture at a reduced cost.